Vacuum surface distillation



R. E, wxLsoN 1,906,033

VACUUM SURFACE DISTILLATION Filed Jan. 2, 195o s sheets-sheet 1 April25, 1933.

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wwlwxw April 25, '1933. R. E. WILSON 1,906,033

VACUUM SURFACE DI STILLATION Filed Jan. 2, 1930 3 sheets-sheet 2 April25, 1933.

Filed Jan. 2, 1930 3 Sheets-Sheet 5 C ONDE/7.55

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Wm w l z @W .H U5 E M n 47% /Z u w 6 A m Q i d 3 AE 47j W w w Ef@ g e sgZ 4 Nw u @F7/..5 .4 x ./PE SM5 e @EN ma M M g4 mmc@ m 9 s m e c e5 WW x7 5 m mm ////F///f// Patented Apr. 25, 1933 fUNl'rsD STATES PATENTOFFICE ROBERT E. WILSON, Ol' CHICAGO, ILLINOIS, ASSIGNOR T0 STANDARD OILCOMPANY (INDIANA), OF CHICAGO, ILILIZIINOISl A CORPORATION OF INDIANAVACUUM SURFACE DISTILLATION Application lcd January 2, 1930. Serial No.417,888.

This invention relates to an apparatus and a process for distillingmineral hydrocarbon oils and it pertains particularly to a vacuumprocess for the distillation and fractionation of heavy high boilingpoint oils.

The object of my invention is to provide a commercial system of vacuumdistillation for mineral oils wherein high boiling point oils may beeffectively distilled 'and fractionated without cracking.

A further object is to accomplish this distillation without theuse ofsteam to effect an economy of heat and to simplify the vacuum systemwhich would otherwise require steam condenscrs and separators.

lA further object is to provide a new and improved method and means ofheating oil whereby the heated surface in the still is entirely coveredby oil and contact between hot surfaces and va ors is prevented.v

A- further ob]ect is to provide means for heating oil in a still byspreading it in a thin lm on vertical tubes heated by a circulatingfluid so that there ,will be a direct application of heat to a rapidlymoving film of oil in such a way as to minimize entrainment.

A furtherv object is to provide a improved arrangement of furnace,condenser.

Another object is to provide means for getting an even flow of oil in afilm throughout the length of vertical tubes and for preventiig apyportion of the tubes from becoming Another object is to provide avac'uum distillation system wherein oil is fractionated by a pluralityof stills under different temperature and pressure conditions andwherein the uniform removal of various fractions is accomplished byrecirculation in each still.

Other objects will be apparent as the detailed description of myinvention proceeds.

My invention is an improvement on the apparatus and process described incoending applications No. 417,585 filed by lmer Il. Payne and Clarke C.Miller and No.

414,931 filed by Elmer H. Payne on December 30, 1929 and December 18,1929 respectively.A

The preferred form of my invention contemplates a forest of verticaltubes mounted new and still and in a still, a condenser mounted in thesame st11l and insulated from the tubes by two trays, one for condensateand one for feed liquid respectively. The feed liquid from the tray isdistributed uniformly in thin films on the vertical tubes and the tubesare heated internally by flue gases, the films being so thin and rapidlymoving that evaporation takes place from the surface of the film withoutthe formation of bubbles. The vapors pass through conduits in the feedplate and condensate plate respectively, and are condensed in the samestil By using vertical tubes, I avoid the spattering and entrainmentwhich would result from the oil dripping through free space; I obtain arapid iiowover the hot surface; and I prevent the vapors produced fromcoming in contact with the hot surfaces.

My invention will be more clearly understood from the followingdescription and the accompanying drawings wherein I have illustrated apreferred embodiment and wherein- Figure 1 is a diagrammatic plan orflow sheetofmy process.

Figure 2 is a vertical section through my improved still. igure 3 is ahorizontal section taken along the lines 3-3 of Figure 2. p

Figure 4 is a horizontal sectiontaken along the lines 4--4 of Figure 2.

Figure 5 is a detail showing in cross section Y one of my improveddistributors.

Figure 6 is a diagrammatic view showing a peferred method for heating myimproved sti Referring to Figure 1, it will be seen that the chargingstock, preferably a reduced crude, is fed through reiiux coils and heatexchanges to iash chambers and thence through the series of evaporatorsor stills. The process will be described in detail after the particularstill structure has been explained.

Referring to Figure 2, it will be seen that the still 10 is acylindrical tank which may be about 10 ft. in diameter and 20 ft. inheight. The still is preferably made in two sections, the lower section11 being secured to the upper section 12 by suitable anges 13. In thelower section of the still, I provide a tubes are closed at the top andprovided with a suitable distributor cap such as 15, having 5 a sawtooth or serrated edge 15A. It is obvious that these serrations may bein the end of the tube itself, the tube eing closed by a suitable plate,thata closed nipple may be used to give the effect of a cup with aserrated upper edge, or that any other form of a distributor may beused.

The lower ends 'of the tubes 14 extend through the base 16 of the stilland are secured thereto by gas tight joints. The tubes are preferably on7 or 8 inch centers, but it is obvious that any of these dimensions maybe varied without departing from my invention. The base is insulated bysuitable material 16A so that the oil in the bottom of the still willnot be over-heated.

The lower section 11 of the still is preferably mounted directly overchamber 17 of furnace 18, the lower ends of pipes 14 communicating withsaid chamber. An exhaust any suitable means, and a series of 3-inchpipes 20 are mounted on said manifold concentrically in pipes 14. Theupper ends of pipes 2() extend to within 4 or 5 inches of the closedends of pipes 14, the lower ends of pipe 20 being mounted on exhaustmanifold. Suitable spacing and reinforcing means may be employed as willbe apparent to those skilled in the art.

The lower section 11 of the still is also provided with an outlet pipe21 for discharging the residue from the still to a sump. I prefer tohave this pipe at the lowermost point so that there will be noaccumulation of oil in the still.

The upper section 12 of the still is provided with an inlet feedl pipe22 for introducing a liquid above distributor plate 23. The distributorplate may be supported in any conventional manner and is provided withdistributor nozzles 24 in alignment with tubes 14 and with vapordischarge pipes 25. Each distributor nozzle 24 is mounted in the ,plate23 as shown in Figure 5 with a restricted orifice 26 spaced from theplate 23 by an inclined or conical wall 27. This construction minimizesthe danger of clogging the orifice by deflecting foreign mattertherefrom. The nozzle 24 may be of l-inch pipe and the orifice may beabout 1A inch, it being understood, of course, that the size of thisorifice will depend upon the rate of flow desired and will thereforevary with different charging stocks.

The vapor discharge pipes are preferably of relatively large diameter,probably about- 6 inches. They are of sufficient height to be above theoverflow wier 28, which is preferably inclined toward the side of thestill 65 as shown in Figure 2, so that any overflow manifold 19 ismounted in said chamber by .f evaporator'and the condenser.

liqpid may be kept out of contact with hot tu es 14 and may beimmediately removed from the still without undue agitation or bubbling.

A distillate receiver is formed in the upper part of the still by meansof plate 29 secured to the walls by any conventional means. A pluralityof vapor tubes 30 extend through this plate to a height suicient toretain the condensate. These pipes are also of relativel large diameterand are preferably provi ed with conical caps or covers 3l to preventany liquid on the condensing coils from dripping through vapor pipes 30.The condensate is drawn from the pool above plate 29, by a suitable pipe.32.

In the top of upper section 12, I mount a condenser coil 33, throughwhich I circulate a. cooling fluid, preferably fresh charging stock. Thecondenser is provided with an inlet 34 and an outlet 35. While it isonly diagrammatically shown in `these drawings, it is understood thatany arrangement of coils may be used which is known in the art.

At the extreme upper part of the still I provide a vapor outlet pipe 36,which may be connected tosuitable coolers and vacuum pumps, ashereinafter set forth.

From the above description, it will be evident that whena liquid isintroduced through pipe 22, it will be distributed by nozzles 24 intocups 15 and will be distributed by their notches 15A onto all sides ofthe tubes 14. The liquid iowing down the sides of tube 14 in a thin filmwill be heated by gases in said tube to drive off the lower boilingpoint components. These components form a vapor which passes throughvapor discharge pipes 25 and vapor tubes 30 to condenser coils 33. Since'the condenser is located close to the evaporating surface, there willbe,-

a relatively small pressure drop between the At the same time, it willbe noted that the liquid on plate 29 and the liquid on plate 23 formheat insulating means between evaporator surface and condenser surface.

Referring more particularly to F igure-'6, I have shown a preferredmethod for heating my improved still. The still 10 may be verticallymounted above chamber 17 of furnace 18 which is separated from thecombustion chamber 37 by baliies 38 and 39, respectively. The exhaustmanifold 19 may be connected to circulator 40, which may dischargethrough valve 41 and pipe 42 into combustion chamber 37 for temperingthe gases in the combustion chamber. Circula= tor 40 forces the exhaustgases through valve 41 and pipe 43 to a heat exchanger 44 for preheatingthe air, and thence through a pipe 45 to the stack 46. The air from thefresh air inlet 47 is preheated in the heat exchanger 44 and directed bypipe 48 and nozzle 49 to support combustion in the furnace chamber 37.The fuel inlet 50 may be designed for liquid or 'gaseous fuel, powderedcoal, etc.

rom the above description, it will be understood that a portion of thehot gases may be continuously recirculated to give better temperaturecontrol and the portion of the gases which are exhausted may deliver uptheirheat to the incoming fresh air. It is understood, however, that Ido not limit myself to the heating means above described and Icontemplate the use of mercury vapors, diphenyl and equivalent heatingmeans. Referring once more to Figure 1, I have designated the stills,chambers, sumps, etc. as A, B, C, etc., and I have designatedthe pumpsand circulators with corresponding letters as a, b, c, etc. Condensatefrom still A is removed by wet vacuum pump a, lthe liquid from sump Gpasses through circulator g, the tar from heat exchanger D is dischargedthrough wet vacuum pump d, etc. Since the legends on Figure 1 areself-explanatory, further description is deemed unnecessary.

The operation of my process may be described as follows: Charging stockfrom tank X is forced by feed pump w through condenser coils in still Aentering about 150 F. and leaving at 250 F. It is next conducted to thecondenser coil in still B, leaving at 355 F., and is then conductedthrough condenser coil in still C, leaving at 440 F. Its temperature isfinally boosted in the tar heat exchanger D where it meets the dischargefrom sump K which may be about 600 F The charging stock at a temperatureof about 550 F. enters a flash chamber E at an absolute pressure of from100 to 500 millimeters, the vapors being removed through condenser Lhaving a dry vacuum pump e for maintaining the reduced pressure andhaving a barometric seal for removing the condensate. Light distillatewill be recovered at this point. From this flash chamber, the hotcharging stock will be conducted to fiash chamber F which is maintainedat 15 to -50 millimeters pressure. The vapors from chamber F arecondensed in condenser M, the liquid being removed by means of abarometric seal and the vacuum being maintained by a dry Vacuum pump f.

From flash chamber F, the charging stockl is introduced as feed liquidin still A, where it is distributed over the vertical pipes 14, andremoved to sump G for recirculation by circulator g. I preferablyrecirculate the stock three or four times so that the feed liquidentering through pipe 22 consists of one part fresh charging stock andfour parts sump stock.

The fresh stock is preferably mixed in the pipe between the circulatorand feed inlet so thatany tendency of the fresh stock 05 to flash may beovercome by its admixture with once-run stock. A portion of the stockfrom sump G is transferred to still B where it is `mixed withrecirculated stock.4 lfrom sump H, fed by circulator L. Similarly, aportion of the stock from sump H is fed into evaporator C admixed withre-run stock from sump K, fed by recirculator cinto still C. The portionof the stock from sump K is continuously discharged into heat exchangerD. from which it is pumped by a vacuum pump d to the tanks containingtar Qor residue. 1

The pressure in still A is preferably about 3 to 10 millimeters, instill B it is 2 to 4 millimeters, and in still C 1 to 3 millimeters. Thestock leaving still A is preferably 450 to 500 F., that leaving still B550 to 575 F and still C 550 to 600 F. I prefer to keep the temperatureof the oil below 600 F., although it is evident that a highertemperature may be-used with a lower vacuum,'a heavier cut beingobtained by higher temperatures.

I contemplate about a 400 difference between hot flue gases enteringtubes 14.- and the residue discharged from the still, the averagetemperature drop of the gases in the tubes being about. 275. It isobvious, however, that these values may be changed to it any particularneed without departing from the spirit of my invention.

Each of the stills A, B, and C, is provided lwith a vapor line leadingtosuitable coolers,

condensers, and dry vacuum pumps. The condensate from still A may belead through cooler N to wet vacuum pump a; the condensate from still Bmay be lead from cooler O to wet Vacuum pump b; and the condensate fromstill C is similarly lead from cooler Pto wet vacuum pump c.

Vhile I have described and shown separate vacuum pumps connected tovarious vapor and condensate discharge lines, it will be evident thatmany of these lines may be connected to suitable manifolds and operatedby a single vacuum pump, and I contemplate such expediency. I alsocontemplate the use of strippers for removing low boilingpointcomponents which may find their way into condensate from thevarious stills or from the heat exchanger. It is obvious that sharpfractionation and stripping may be obtained by any known process orapparatus and may be inserted at any point in my arrangement.

The exteriors of all of the still, flash towers, heat exchangers, sumps,conduits, and other parts of my apparatus are lagged or thermallyinsulated, thenecessity of such insulation being obvious.

The rate of feed will depend on the amount of recirculation required tocompletely drive olf a fraction of given boiling point. This will dependon the charging stock and will have tov be determined by the operator.In no case should the oil be fed so fast t-hat it does not adhere to thetubes because any spattering might cause entrainment.

While I have described in detail a pre- 5 ferred embodiment of myinvention, and have given certain values of temperatures and pressure,it is understood that these are given by way of example and I am notlimited thereto, except as defined by the appended claims. The termvacuum is used in these claims to designate a reduced absolute pressureof about the order mentioned in my specification, and does not, ofcourse, mean absolute vacuum.

I claim:

l. In distillation apparatus, a still, a plurality of tubes in saidstill, means for heating said tubes, and means for distributing oil in afilm on said tubes comprising a plate having distributor nozzles alignedwith said tu es, and h-aving vapor discharge conduits between saidnozzles for the removal of vapors surrounding said tubes.

2. In combination a furnace, a still mounted adjacent to said furnace, aplurality of vertical tubes extending in said still and communicatingwith said furnace, said tubes being closed in said still, means forflowing oil in a film downwardly over the exterior surface of saidtubes, and means to circulate hot fluids from said furnace through saidtubes including an exhaust manifold and plurality of tubes connectedthereto and mounted substantially concentric with said first-namedtubes.

3. In combination a furnace, a still mounted on said furnace, aplurality of pipes opening into said furnace and extending in saidstill, pipes mounted inside of said firstnamed pipes and connected to amanifold, a circulator connected to said manifold, conduits from saidcirculator to said furnace whereby the circulator forces gases into thefurnace, from the furnace through the outer tubes, and thence throughthe inner tubes and the manifold back to the circulator.

4. In oil distillation apparatus, a still, a plurality of vertical tubesin said still, means for heating said tubes, means for distribut- U ingthe oil in a film on said tubes, comprising a plate having distributornozzles aligned with said tubes, means for maintaining a body of oil onsaid plate, said plate having vapor discharge conduits therethrough andextending above said body of oil for the removal of vapors distilledfrom the oil on the tubes.

5. In distillation apparatus, a still, a plurality of vertical tubes insaid still, means for heating saidy tubes, means for distributing oil ina film on said tubes, comprising a plate having distributornnozzlesaligned with said tubes, means foi` maintaining a body of oil on saidplate, said nozzles arranged to be submerged in said oil and beingconstricted at the upper ends thereof, said plate having vapor dischargeconduits therethrough and extending above said body of oil for theremoval of vapors distilled from the oil on the tubes.

6. In oil distillation apparatus, a still, a plurality of vertical tubesin said still, means for heating said tubes, means for distributing theoil in a film on said tubes, comprising a plate having distributornozzles aligned with said tubes, means for maintaining a body of oil onsaid plate, said plate having vapor discharge conduits therethrough andextending above said body of oil for the removal of vapors distilledfrom the oil on the tubes, and condensing means superposed above thevapor conduits for partial condensation of the said vapors.

7. In distillation apparatus, a still, a plurality of vertical tubes insaid still, means for heating said tubes, said means comprising tubesmounted within said first named tubes and connected to a manifold, meansfor circulating a heating fiuid upwardly through said first named tubes,then downwardly through said inner tubes and thence into said manifold,means for distributing oil in a film on said first named tubes,comprising a plate having distributor nozzles aligned with said tubes,means for maintaining a body of oil on said plates, said plate havingvapor discharge conduits therethrough and extending above said body ofoil for the removal of vapors distilled from the oil on the tubes.

Signed this 26th day of December, 1929, at Chicago, Cook County,Illinois.

ROBE-RT E. WILSON.

